def str_reverse(s) -> str:
    """
    reverse a str
    :param s: the string to reverse
    :return: str
    """
    return s[::-1]

def sub_str(s, x, y) -> str:
    return s[x:y]

if __name__ == '__main__':
    s = "0123456789"
    print(str_reverse(s))
    print(sub_str(s, 3, 5))